Rounding Off — Prelims Strategy

Prelims Strategy

Read the precision instruction before changing any digits. Identify whether it asks for decimal places, significant figures, a nearest unit or a rough estimate. Apply the stated tie-breaking convention; for ordinary positive school exercises, use the usual half-up rule unless another rule is supplied.

Keep unrounded intermediate values when feasible and round the final result once. If mental estimation is enough to distinguish the options, use convenient nearby numbers and note whether the estimate is likely above or below the exact result. When alternatives are close, tighten the calculation rather than treating a rough estimate as decisive.

For questions about an original value that has been rounded, construct the full rounding interval. Endpoint inclusion depends on the specified convention, so do not automatically use symmetric closed bounds. For sums or products of approximate measurements, consider how errors combine. Finish by reporting the requested precision and checking whether the uncertainty could change the selected answer or a threshold decision.